Method for increasing the effectiveness of liquid-spray cooling



United States Patent METHOD FOR INCREASING THE EFFECTIVENESS This invention relates to a method for liquid-spray cooling of metal whereby" increased cooling rates may be achieved without requiring a greater volume of liquid, or conventional cooling rates with less liquid.

Liquid-spray cooling is used extensively in industry, particularly in the processing of metals. Spray cooling of silicon-steel stn'p between the last roll stand and the coiler is an example of an application in which rapid cooling determines the metallurgical quality of the product. In other instances, preferential cooling is advantageous in making products desirably having hard and soft portions, such as railroad-car wheels and rails where hard wearing surfaces and less hard webs are preferred.

High cooling rates from temperatures in the neighborhood of 1000 F. and higher are frequently desirable for obvious reasons but have required excessive volumes of the coolant, usually water. In addition, there are applications where difierential cooling rates in spaced areas of the same part are advantageous. It is accordingly the object of our invention to provide a method of increasing the effectiveness of liquid-spray cooling. A further object is to provide such a method which is simple and inexpensive and may be applied selectively to different portions of the surface of an article or product being processed.

A complete understanding of the invention may be obtained from the following detailed explanation of the 3,250,650 Patented May 10, 1966 coating baked on in place. The concentration of the oxide in the suspension should be from 1 to 10%. Regardless of the method by which the-oxide coating is applied, liquid-spray cooling of the heated metal will effect a temperature reduction in the coated area at a rate much greater than that which results from liquid spraying of uncoated metal at the same temperature. The coating may be applied by painting -it on, by spraying or by blowing.

The following are typical examples of our method:

In one trial, a carbon steel plate (8 x 6' x with thermocouples embedded at various depths in its interior was used. The thermocouple outputs were recorded on a sensitive multiple-channel recording oscillograph. The,

were coated with the oxides listed in Table I below by methods a, b or c referred to above, viz.:

Method a.The steel plate was coated with a water slurry of the metallic'oxide (concentration approximately before it was heated.

Method b.The steel plate was coated after heating to a temperature of 2200 F. 50% sodium silicate in powdered form was used as the bonding agent.

Method c.-A water suspension of the metallic oxide (concentration 5%) was sprayed on the hot sample.

The cooling rates given in the table were obtained by analyzing the thermocouple data, for the various coatings applied with the three methods listed above. These cooling rates represent average values obtained over a cooling period of 14 seconds.

Aluminum Oxide Bentonite 1 Si 2,

Cuprous Oxide Lime (40% Ca(OH) 20% g( )i) Magnesium Oxide Marking pencil ('IiO and C210) Titanium Oxide Metal Surface Not Coated 1 5% suspension of bentonite sprayed on hot sample.

preferred practice and some specific examples thereof. Generally stated, our invention consists in applying to metal which has been or is to be heated, a tightly adherent coating extending continuously over the area which 60 is to have the highest cooling rate, of an oxide of a metal selected from the group: aluminum, calcium, copper, magnesium, silicon, titanium.

The oxide coating may be applied to the surface of the metal before the latter is heated as a water slurry of from 25 to 80% concentration by weight, preferably about 50%. It may also be applied after the metal has been heated, as a water suspension or as a dry powder with an admixture of a bonding agent such as sodium- Since bentonite contains silicates, they provide adequate bonding and thus a separate bonding agent is not required. The lime as applied, of course, is not an oxide but is converted thereto by the heat of the metal to be cooled.

It is evident from the foregoing data that our invention produces a very marked increase in the rate of liquidspray cooling of heated metal, as compared with the figures for untreated metal (last line of Table I).

Although we have disclosed herein the preferred embodiment and practice of our invention, we intend to cover as well any change or modification therein which may be made without departing from the spirit and scope silicate powder. When the water suspension is employed of the invention.

it may be applied so the water content thereof efiects spray cooling while the solid oxide particles form a We claim: 1. An improved method of cooling a metal article from temperatures of at least about 1000 F. which comprises providing on a surface of said article a continuous, adherent coating of an oxide of a metal from the group consisting of aluminum, calcium, copper, magnesium, silicon and titanium and subjecting the coated surface to a spray of cooling liquid.

2. A method as defined in claim 1, characterized by coating the surface by painting it with a water slurry of the oxide.

3. A method as defined in claim 1, characterized by coating the surface by spraying it with a water suspension of the oxide.

4. A method as defined in claim 1, characterized by coating the surface by discharging onto it a blast containing particles of the oxide mixed with powdered sodium silicate.

References Cited by the Examiner UNITED STATES PATENTS DAVID L. RECK, Primary Examiner,

WINSTON A. DOUGLAS, Examiner 

1. AN IMPROVED METHOD OF COOLING A METAL ARTICLE FROM TEMPERATURES OF AT LEAST ABOUT 1000*F. WHICH COMPRISES PROVIDING ON A SURFACE OF SAID ARTICLES A CONTINUOUS, ADHERENT COATING OF AN OXIDE OF A METAL FROM THE GROUP CONSISTING OF ALUMINUM, CALCIUM, COPPER, MAGNESIUM, SILICON AND TITANIUM AND SUBJECTING THE COATED SURFACE TO A SPRAY OF COOLING LIQUID. 